Police have arrested a 21-year-old Dorchester man who allegedly fled after an incident in Town Field that later led to a 19-year-old man exchanging gunfire with police before being fatally shot.

Ernest Watkins was located and arrested late Tuesday night near Melville Avenue and Dorchester Avenue, Boston Police said.

He was arraigned in Dorchester District Court on charges of assault by means of a dangerous weapon, unlawful possession of a firearm, unlawful possession of ammunition, and discharging a firearm within 500 feet of a building, according to the Suffolk District Attorney's office. he is held on $25,000 bail and release terms include wearing a GPS monitor and remaining under home confinement.

"The defendant is also charged as a Level 1 armed career criminal based on his 2015 conviction for involuntary manslaughter in connection with the 2012 homicide of 39-year-old Cherby LaJoie," the DA's office noted. "Prosecutors in 2015 recommended that the defendant be sentenced to 12 to 15 years in state prison for his role in LaJoie’s stabbing death; Judge Kenneth Fishman sentenced the defendant to an incarcerated term of four to five years."

Watkins is allegedly one of two suspects who ran from police responding to reports of gunfire around Town Field around 5:15 p.m. Monday. The police saw two black men fleeing the scene, one of whom fled up Mather Street and escaped. He was later identified as Watkins.

The second man — identified Wednesday as Jaymil Ellerbe, 19 years old, of Dorchester — ran to Penhallow Street and allegedly ignored calls from officers to drop his gun, instead opening fire. An officer who was part of the city wide bicycle unit shot and killed the man.

District Attorney Rachael Rollins said in a statement Tuesday: “The sequence of events last evening that began with a shooting in a crowded park in the Fields Corner section of Dorchester and ended with a loss of life on Penhallow Street has left the city shaken.”
 
“I am thankful for the immediate response of the Boston Police Department and that none of those officers were injured. I would be remiss if I did not thank the many witnesses from the community who came forward to aid investigators at the scene.  If there is anyone in the community with additional information, please bring that to my office directly.   
 
“I also acknowledge that a family has lost its loved one; to them, I express my sympathy.  As your District Attorney, it is my office that holds exclusive jurisdiction over any death investigation, including police-involved shootings.  I assure that family, members of law enforcement, and this community that there will be a complete, impartial, and transparent review by my Discharge Integrity Team, and we will make our findings available to the public. As we lead our independent investigation into the events that unfolded yesterday, we ask for patience and calm; violence or the threat thereof have no place in our community.“