By DAVID WARREN and CLAUDIA LAUER ,  Associated Press

DALLAS (AP) — A 36-year-old man with a criminal history fatally shot his roommate before shooting a neighbor and a responding paramedic during an attack in a Dallas neighborhood that prompted police to barricade the area for hours, investigators said Tuesday.
Derick Lamont Brown was acting erratically at his home before forcing his 67-year-old roommate into a back room and fatally shooting him on Monday, said Randy Blankenbaker, Dallas's police assistant chief of investigations.
A neighbor heard the gunshots and came outside. Brown, armed with a semi-automatic rifle, shot the neighbor and then opened fire on emergency responders, hitting one of the paramedics, Blankenbaker said. Both the neighbor and paramedic were critically wounded.
Brown fired at responding police officers at they tried to take cover, including one officer who sustained an injury to his calf, possibly from gunfire, the assistant chief said. Blankenbaker said the shooting was initially reported as a possible suicide, which added to some of the confusion as officers arrived.
Brown turned and pointed his rifle as one officer approached, prompting another officer to shoot and injure Brown, Blankenbaker said. Brown then retreated to his home.
Officers carried the injured paramedic into a squad car and rushed him to a hospital. The neighbor, whose name wasn't released, was also taken to the hospital. Both sustained critical injuries.
"All of these officers' actions are more than commendable. They should be considered heroic," Blankenbaker said.
The attack prompted police to block access to the area until a police robot searched Brown's home, where it found Brown and his roommate dead.
The paramedic underwent surgery Monday and was in critical but stable condition at Baylor University Medical Center, Dallas Mayor Mike Rawlings said during a news conference Monday. Rawlings didn't give details of the paramedic's injuries, but said "he is going to have to undergo extensive medical treatment to get him back up to par."
The neighbor also was in critical condition at the hospital Monday. Police didn't provide an update on his condition Tuesday.
Blankenbaker said Brown's criminal history includes charges of aggravated assault, driving while intoxicated and illegal gun possession. Police said Brown was well-known by law enforcement because of his "excessive arrest history."Dozens of police vehicles swarmed the mostly residential area after the shooting was reported near a local Fire Training Academy. Several people from a nearby neighborhood and some relatives of people who live in the barricaded area gathered at a nearby gas station to await updates from police.
A 33-year-old woman waiting in the shade of a gas station across the street from a police barricade told The Associated Press that her mother lived in the neighborhood and saw SWAT teams arrive Monday.
Brenda Salazar said she was headed to the area to visit her mother when she heard about the shooting on the radio. She called her mother, who told her she didn't hear any shooting but "saw the SWAT guys and police setting up and going into the neighborhood."
Salazar said her mother was OK and was watching the news, "but this stuff happens here all the time."
Texas Gov. Greg Abbott released a statement saying his prayers were going out to all those affected.
FBI agents and officers with the Bureau of Alcohol, Tobacco, Firearms and Explosives also were in unmarked vehicles waiting at intersections in the neighborhood. Officials from the local fire department and parks department passed out water and Gatorade to officers blocking the roads.