He remained in custody Wednesday awaiting a bond hearing.
The victim of the shooting has been identified as William Howard Green, 43, of Washington, D.C. The department did not release Green's race, which WBAL in Baltimore reported is departmental policy.
Photos obtained by The Washington Post and other media outlets show that, like Owen, Green is black.
Prince George’s County police Chief Hank Stawinski described the arrest, which took place within 24 hours of the shooting, as an “unprecedented” one for his department. He said the announcement was the most difficult of his tenure as chief.
"I am unable to come to our community this evening and offer you a reasonable explanation for the events that occurred last night," a grim-faced Stawinski said Tuesday during a news conference. "I have concluded that what happened last night is a crime."
The fatal encounter began around 7:20 p.m. Monday in Temple Hills, where Owen and another officer responded to a call about a traffic accident in which Green was accused of striking multiple vehicles. They found Green parked nearby, according to authorities.
Police officials initially said the officers reported that Green was possibly under the influence of drugs, claiming to have smelled phencyclidine, or PCP, when they approached him. Also known as “angel dust,” PCP is a hallucinogen associated with sometimes violent behavior in users.
There was also at least one unidentified witness who claimed to have seen a struggle in the patrol car, where Green was seated in the passenger front seat next to Owen.
Stawinski on Tuesday walked back those earlier statements, saying PCP does not appear to have been involved in the incident and that the department’s preliminary investigation could not corroborate the claim of a struggle between Owen and Green. Initial reports that Green was belted into the seat are also in question.
Witness footage of Green's initial encounter with the officers, obtained by Fox 5 in Washington, showed him sitting calmly in the driver's seat of his vehicle. The news station reported he was in police custody for at least 20 minutes before he was shot to death.
A news release regarding Owen's arrest said he was shot as the officers awaited the arrival of a drug recognition expert.
"As they waited, Owen got into the driver's seat of his cruiser and was now seated next to Green," the release said. "A short time later, for reasons that are now at the center of the investigation, Green was shot seven times by the officer's duty weapon."
Owen and the second officer pulled Green from the cruiser and began offering medical aid, but he was pronounced dead at a hospital a short time later.
Tuesday’s news release stated that Green’s location in the front passenger seat of Owen’s patrol car was within departmental policy.
"One officer may transport one arrestee, who will occupy the right front seat," the policy states. "For vehicles equipped with transport partitions, arrestees will occupy the right rear seat."
Owen’s car did not have a partition, the news release said.
The shooting was not caught on body camera because Owen had not been assigned one, the chief said. State's Attorney Aisha Braveboy said only about 80 of the department's more than 1,500 officers are equipped with body cameras, according to the Post.
“There are no circumstances under which this outcome is acceptable, and I want to extend my heartfelt sorrow and sympathies to the Green family,” Stawinski said Tuesday. “You have my assurance that all of our methods and practices will be examined as this investigation proceeds, and I will be looking to independent eyes in the coming days to provide further insight into these circumstances.”
Watch Tuesday’s news conference below, courtesy of Fox 5.
Other county officials also spoke about the arrest.
“There is absolutely nothing acceptable about this incident,” said Prince George’s County Executive Angela Alsobrooks, who began her remarks by offering her condolences to Green’s family.
“This has been an exceedingly difficult day for all of us, for this community, for this department and most especially for the family of William Green,” Alsobrooks said. “We have really been grief-stricken with the family … we as a community have grieved with this family today.”
Sandra Mathis, who identified herself as Green's fiancée, told Fox 5 the family has "questions with no answers."
"We need to know what happened to William Green," Mathis told the news station. "His life matters. He was loved."
Mathis' son, John Mathis, 19, told the Post the slain man worked as a Megabus luggage loader. Green was due for a promotion to dispatcher Tuesday, the day after his shooting, the teen said.
Green was also a member of the Temple of Praise Church in D.C., John Mathis said.
The family has hired Baltimore attorney William "Billy" Murphy to represent them, the Post reported. Murphy also represented the family of Freddie Gray, a 25-year-old Baltimore man who died April 19, 2015, of injures he suffered while in police custody.
Though six Baltimore officers involved in Gray's arrest were charged in the case, none were convicted. The U.S. Department of Justice declined in September 2017 to bring charges against the officers.
Murphy told the Post that Green’s shooting is one of the worst police-involved cases he’s seen.
"I have seen a lot of horrible fatal police shootings, but this one is in the Top 10," Murphy said.
Along with the family, the ACLU of Maryland is calling for “complete transparency” from Prince George’s County officials.
"There is no reason why a handcuffed person should ever be shot multiple times by a police officer, let alone shot multiple times inside a patrol car," the organization said in a lengthy written statement that pointed out the Prince George's County Police Department's history of police-involved shootings.
"It is completely unacceptable for a police department that is currently under investigation by the Department of Justice -- and being sued by its own black and Latinx police officers for fostering a culture of racism -- to still not have body-worn cameras equipped on all of their officers, especially given that PGPD's BWC (body-worn camera) program was rolled out in 2017," the statement reads. "It is absolutely senseless for full transparency to not be a number one priority for this department. It should have been a top priority years ago, but these recent tragic events only make this need more urgent."
Braveboy said Tuesday that the charges against Owens will be brought before a grand jury in the coming months.
"There will be a thorough investigation into this case," Braveboy said. "We are very early in that process but at the conclusion of that process, final charging decisions will be made."
Green's death is the third shooting Owen has been involved in -- and the second fatal, on-duty shooting, the Post said. Owen fatally shot Rodney Deron Edwards, 35, of Landover the night of Dec. 17, 2011, after Edwards, who had been lying in some grass on the side of a roadway, threatened him with a revolver after Owen stopped to offer him assistance.
Owen, who had been an officer for two years at that time, was driving an unmarked police van as he left a Toys for Tots event that night, the Post reported at the time.
Owen was off-duty in 2009 when a would-be robber shot at him outside his home, the newspaper reported. The officer, who was not struck by the gunfire, fired back in self-defense.
Following the shootings, Owens was taken off patrol for a while and spent time as a spokesman for the department, the Post reported.