(Reuters) – Las Vegas police presented a third version on Friday of the timeline of events for the Las Vegas gunman who killed 58 people and himself, saying they responded immediately to the deadliest mass shooting in modern U.S. history.

Clark County Sheriff Joseph Lombardo, who oversees the Las Vegas police department, told reporters that gunman Stephen Paddock shot at Mandalay Bay hotel security guard Jesus Campos outside his room on Oct. 1 at about the same time he opened fire on the more than 20,000 concertgoers at an outdoor venue.

Previously, police said that Paddock shot Campos six minutes before he started firing on the crowd, raising questions as to whether police and hotel security could have acted faster to prevent casualties in the attack.

“Nobody is attempting to hide anything. The dynamics and the size of the investigation require us to go through voluminous amounts of information in order to draw an accurate picture,” Lombardo said of the changing timeline.

The police account is similar to one given on Thursday by the hotel operator MGM Resorts International (MGM.N), which said in a statement that Paddock opened fire on Campos and the crowd at the same time or within 40 seconds.

Campos was shot in the leg when Paddock strafed the hallway with about 200 bullets, police said.

Paddock, who placed cameras in the hotel hallway to monitor activity, also injured 546 people before killing himself. No motive for the attack has been made public.

The third timeline could affect claims brought by some victims that depend on the hotel’s allegedly delayed response after Campos was shot. One attorney told Reuters MGM may have acted quickly but questioned whether “reasonable precautions” were in place.

Most of the wounded have been discharged from hospitals, but 45 were still hospitalized, some with critical injuries, Lombardo said.

Lombardo said law enforcement had acted heroically on the night of the attack and that he was angered by the criticism his department has received over its investigation.

“In the public space, the word incompetence has been brought forward and I am absolutely offended with that characterization,” he said.

Aaron Rouse, special agent in charge of the Las Vegas Federal Bureau of Investigation office, said there was no information Paddock was a member of an extremist group. Rouse added the FBI has hundreds of agents on the case working with local law enforcement.

“Nothing will be overlooked. We have made significant progress,” Rouse said. Neither Lombardo nor Rouse took questions.