Darris Kimbro works for the New York Police Department and is the son of Lacey Kimbro, an old friend of Luke Cage. Darris was on patrol in Hell's Kitchen when he was taken captive by Hand ninjas (along with several other citizens) as Daredevil had taken control over Hell's Kitchen.
Darris Kimbro was created by Jeff Parker and Declan Shalvey and first appeared in Thunderbolts #148.
Although Darris Kimbro died in his first appearance, his death served as a plot point in subsequent Thunderbolts issues and led to his murderer being kicked off the team.
Major Story Arcs
When Luke Cage discovered that Darris had been captured by The Hand, he sent the Thunderbolts to intervene and free Darris and the other captives. Unfortunately, Cage was involved in confronting Daredevil meaning that he left Fixer and Songbird in charge of the team.
While battling The Hand, both Fixer and Songbird were incapacitated, and only Crossbones and Ghost managed to locate the prisoners. While fighting Hand ninjas, Crossbones began to display new powers (which he had received when he was accidentally exposed to Terrigen Crystals on a previous mission) and began firing intense beams of heat from his face.
Making short work of the Ninjas, Crossbones turned to Darris and instead of saving him used his new found powers to murder him on the grounds that he was a cop. The rest of the Thunderbolts arrived just afterwards and Crossbones' powers faded away, much to his dismay. The team saw Darris dead body laying on the floor, which Crossbones claimed the Hand were responsible for, Ghost being the only one who knew the truth which he decided to keep to himself.
When some of the Thunderbolts attempted to escape the Raft, they were hunted by the Avengers. While Ghost and Juggernaut eventually resolved to peacefully return to the Raft with the Avengers, Crossbones continued to fight and attempted to murder Steve Rogers. As the Avengers and Thunderbolts rushed to stop Crossbones, Ghost revealed his knowledge of Crossbones' murder of Darris to both the Avengers and Thunderbolts.
The teams arrived just in time to see Steve Rogers had managed to beat Crossbones and the murderer was taken back to the Raft and ejected from the Thunderbolts Program and forced to sit out the rest of his life sentence in his cell.
Powers and Abilities
Darris Kimbro has no superhuman abilities. He has had police training, but due to being a beat cop, presumably hasn't had all that much real experience in combat and firearms.