He came out of his fourth-floor office in the Engineering 4 building as did his colleague Christopher Lynch. They looked at each other.
"What was that?" Mal said.
"That's gunshot," Lynch replied.
But neither Mal nor Lynch, both professors of mechanical and aerospace engineering, knew that at the time.
Lynch did know that Klug, a 39-year-old engineering professor and devoted family man, described by colleagues as both brilliant and kind, would never take his own life. He figured a shooter was inside.
And he knew that more than a dozen faculty and staff members were on the floor at the time.
So he went to Klug's office and held the door shut.
"If he had stepped out," Lynch said of the shooter, "we'd all be in trouble."
After that, Lynch heard a third shot inside. Then silence. Lynch assumed the shooter had killed himself.
Within minutes, the professors said, police converged and cleared out the floor. Lynch gave the door key to police without looking inside and left. He said he did not feel Sarkar try to open the door after the shooting but was sure the gunman had heard the yells from the hallway to clear out and that police had been called.
Mal credits Lynch with saving his life. Besides holding the door shut, Mal said, Lynch also shouted at him and other colleagues to return to their offices and close their doors.
Sarkar had been armed with two semiautomatic pistols and extra magazines, and was "certainly prepared to engage multiple victims," LAPD Chief Charlie Beck said.
"If he had come out with a loaded gun, I don't think I'd be alive," Mal said of Sarkar. "Chris Lynch's presence of mind and quick action saved us."
Lynch, speaking to The Times on Friday in his first public comments about the shooting, confirmed Mal's account reluctantly, saying he wanted the focus to remain on Klug and his family.
He also praised his colleagues in the mechanical and aerospace engineering department for their calm actions during the crisis. He and Mal said that Angie Castillo, the department manager, and Tsu-Chin Tsao, department chair, acted swiftly to call 911 and support the group throughout the harrowing day and aftermath.
"Not a single person panicked," Lynch said. "Everyone acted professionally."
The two men both said that Sarkar's allegation that Klug had stolen his computer code was groundless. Lynch said all UCLA employees and graduate students sign over any intellectual property developed there to the university and, if it is subsequently licensed, enter royalty agreements to share in the profits.
Mal said it was "common practice" for computer codes developed by one student to be used by others. One of his former students, now working at the Jet Propulsion Laboratory, still consults with current graduate students who continue to use his code involving the impact of outside forces on new materials being used in aerospace.
"There just isn't an issue worth discussing here," Lynch said. "This is what a very sick mind dredged up. It's delusional."
Both men said that Sarkar had enrolled in their classes several years earlier but left little impression. Mal said Sarkar was quiet and reserved and would not even greet him when the two men passed each other, which the professor found somewhat odd since both hail from West Bengal in India and speak the same language.
He also said it was likely that Klug never knew of Sarkar's animosity toward him. If he had, Mal said, Klug would probably have consulted him for his Indian cultural insights and years of experience; the two men were close as Mal had headed the search committee that hired Klug in 2003.
"This whole thing is so incredible and bizarre because Bill is the least likely to have some conflict with students," Mal said. "He was so very caring."
Sarkar is also believed to have killed his wife in Minnesota before driving to UCLA.
Follow me for education news at @teresawatanabe