DALLAS—Dallas police Detective Paul Bentley, who helped arrest presidential assassin Lee Harvey Oswald at the Texas Theater, always had a ready retort for those who didn’t accept the official story that Oswald acted alone.

“What does conspiracy do?” Bentley would say. “It sells.”

Bentley died Monday of natural causes in his Dallas home, said his grandson, David Ottinger. He was 87.

Bentley worked for the Dallas Police Department for 21 years, starting as a patrol officer and retiring as a detective five years after the assassination of President Kennedy.

He played a supporting role on Nov. 22, 1963, originally responding to Oswald’s fatal shooting of Dallas police Officer J.D. Tippit. Bentley and other officers tracked Oswald to the Texas Theater, arresting the assassin after a brief scuffle.

“The fight broke out on the main floor,” said Gary Mack, curator of The Sixth Floor Museum at Dealey Plaza. “Bentley was up in the balcony. He raced down to help and piled on because Oswald punched an officer and pulled a gun.”

In a well-known photograph taken just after the arrest, Bentley is wearing a suit with his hair slicked back and a cigar in his mouth, escorting Oswald out of the theater. Oswald appears to have a cut on his forehead, which Bentley said came from his Masonic ring, Ottinger said.

His grandson described Bentley as an honorable and decent man.

“As time went by, it became an important piece of history, but he always said he was just doing his job that day,” Ottinger said. “He never viewed himself as a hero or anything of that nature.”

Besides the arrest, Bentley had another connection to Oswald. Bentley’s brother-in-law, L.C. Graves, who died in 1995, was one of the officers escorting Oswald when the killer was shot to death by Jack Ruby. Graves can be seen to Oswald’s left in a famous photograph of the shooting.

“My grandpa used to say to his brother-in-law, ‘I arrested him and you let him get shot,”’ Ottinger said.

Bentley is survived by his wife of 66 years, Mozelle; a son, James; and his grandson. A daughter, Barbara, died in 1973.

A burial service is scheduled for 10 a.m. Thursday with a memorial service to follow.