Elgin police shot and killed a pit bull with a history of dangerous behavior Monday night after it attacked a neighbor’s dog – also a pit bull.

Around 6:30 p.m., the dog went into a backyard in the 300 block of Fulton Street and began attacking another dog who lived there, police said, prompting a resident to call for help.

Jose Diaz, who lives with the attacking pit bull, Rocco, arrived when police did, as  he works nearby. His son, 19-year-old Christian Diaz, owns Rocco. He had brought Rocco to his girlfriend’s house, which is why he was outside in a kennel, Jose Diaz said.

Somehow the dog was able to escape and went into the neighbor’s yard with the other pit bull, he said.

Diaz said he tried to keep the two dogs apart with a folding chair, but couldn’t stop the fight. In the process, Diaz suffered a minor bite from the other pit bull, he said.

“After (Rocco) saw I got bit…he went after the dog. That’s when he decided to go all out at him,” Diaz said.

At that point, no one could separate the dogs, so police shot Rocco, who was killed instantly, police said.

“There’s nothing we could do,” Diaz said.

The other, injured dog was taken to an animal hospital for treatment, but his injuries were not life threatening, police said.

Animal control officers still are investigating the incident, and police said charges are pending.

Christian Diaz has seven previous citations in the past two months relating to Rocco, police said. The tickets include leaving Rocco off the leash, and for Rocco charging other people and dogs, police said.