LOS ANGELES — Determining a motive for the man who committed one of the deadliest mass shootings in modern history continues to be an exasperating task for investigators. They have interviewed many of Stephen Paddock’s relatives and friends, and examined his travel, financial and health history. But they have yet to find anything that points to what drove him to kill 58 people at a concert in Las Vegas on Oct. 1.

On Wednesday, information emerged that adds to the complexity of the case. Mr. Paddock apparently removed the hard drive from at least one computer found in his room at the Mandalay Bay Resort and Casino, according to a law enforcement official.

Additionally, housekeepers had visited Mr. Paddock’s room, where he fired on the crowd below, more than once in the days before the shooting, but did not notice any sign of his large stockpile of weapons. He also ordered room service at least once, according to people with knowledge of the security response inside the hotel.

Separately on Wednesday, Mr. Paddock’s brother was arrested at an assisted living facility in Los Angeles on charges of possessing child pornography.