“The law does not require that you wait to be struck before you take action. Had this resulted in a hands-on fight and a struggle for Agent Valdivia’s gun, only God knows what could have happened,” Bonsib said after a judge ordered the agent released from custody.

After the hearing, the county’s top prosecutor declined to explain why his office concluded that the shooting was not justified.

“We would not have brought the charge if we thought that it was protected by law,” Montgomery County State’s Attorney John McCarthy told reporters. “To explain all of the reasons why we came to this conclusion would be effectively for me to give you a closing argument as to a five-month investigation. This is not the appropriate time.”

Valdivia shot and wounded the man from a distance of roughly 2 to 3 feet (0.6 to 0.9 metres) after repeatedly telling the man to back up, county prosecutor Robert Hill said in court.

The man had approached Valdivia on a train, sat across from him and asked the agent for money, Hill said. The man muttered expletives and began to walk away when the agent said he didn’t have any money to give, the prosecutor added.

“Watch your mouth,” the agent told the man, according to Hill.

After the man turned and approached him again, Valdivia pulled a gun from a holster and shot him, the prosecutor said. Another passenger was in the agent’s line of fire, about 15 feet away, but wasn’t harmed, Hill added.

A grand jury indicted Valdivia on charges including attempted second-degree murder, first-degree assault and reckless endangerment.

Valdivia turned himself in to local authorities at a county jail on Tuesday morning. Montgomery County Circuit Court Judge Joan Ryon agreed to release him on personal recognisance. Prosecutors did not object.

The wounded man had part or all of his spleen, colon and pancreas removed during surgery after the shooting, according to Hill.

Bonsib said his client has had “an impeccable personal and professional background”. He joined the bureau in 2011, and at the time of the shooting, was providing “operational guidance and programmatic oversight” of FBI investigations targeting racially motivated and anti-government extremists.

Valdivia was on his way to work on the morning of the shooting when the man approached him.

Bonsib said court records show the wounded man has a criminal record with a history of unpredictable and violent behaviour, including an 2019 incident in which the man allegedly attacked and threatened to kill somebody at a Metro station.

Prosecutors questioned the relevance of the wounded man’s record since the agent didn’t know about it and hadn’t met him before the morning of the shooting.

The indictment names the man who was shot and a second passenger, who it identifies as the victim of the reckless endangerment charge for being in the line of fire.

In a statement on Tuesday, a spokeswoman for the FBI’s Baltimore field office said the bureau was aware of the charges and is fully cooperating with the investigation.

“As is customary following a shooting incident, this matter will be subject to internal review,” spokeswoman Joy Jiras said.

The Metro Transit Police Department said in December that it had reviewed video footage and taken statements from Metro employees, passengers and others.

The Medical Centre station serves the National Institutes of Health and Walter Reed National Military Medical Centre.