"I have no answer to why or how" the attack occurred, said Butler, 41, a former ICE agent. "Everything was coming together. Everything was peachy, peachy, lovely."
Chisem's son did fairly well at a nearby high school and liked to play video games, he said.
"He has to go through all this now," a tearful Butler said. "His father loved him so much. I'm in disbelief."
Butler said he and Chisem became friends while they were in the Navy and Chisem also had two older daughters and worked at Los Angeles International Airport on contraband and smuggling investigations.
Chisem was the godfather of Butler's kids and the two played chess and golf together. They also argued about football teams: Chisem favored the San Francisco 49ers, Butler liked the Dallas Cowboys.
"I loved him like my own brother," Butler said. "He would do anything for anybody."
Fellow agents arrived at Chisem's house, lined the driveway and saluted as the body, covered by an American flag, was wheeled to a coroner's van.
"This is a difficult time for ICE, especially for the family and loved ones of the agent. Please keep them in your thoughts and prayers,' ICE Director John Morton said in a statement.