WASHINGTON (Reuters) - The FBI will beef up its procedures for documenting and following up on investigative leads after mishandling detailed tips about the teenager who shot and killed 17 people at a high school in Parkland, Florida, a top official said on Wednesday.

Speaking publicly before a U.S. Senate panel for the first time since he was elevated to the No. 2 spot at the Federal Bureau of Investigation in January, Acting Deputy Director David Bowdich testified that his agency should have done more to investigate and respond appropriately to tips about alleged gunman Nikolas Cruz.

One of those tips, received in January just weeks before the shooting, came from a caller who warned the FBI she feared Cruz, 19, might try shooting up the school and had exhibited disturbing behavior, such as mutilating animals and expressing a desire to kill.

“Did the FBI reach out to law enforcement to give them a warning about Cruz?” Senate Judiciary Committee Chairman Charles Grassley asked Bowdich.

“Sir, we did not,” Bowdich said. “I do not know why the call taker did not do so.”

Wednesday’s hearing came as high school students across the United States walked out of their classrooms in protest to demand stricter gun laws.

The shooting in Florida has reignited a long-standing debate in Congress over gun control, with many young people calling on state and federal officials to take steps such as banning assault-style rifles, raising the age for purchasing firearms and improving the background check process.

But despite overwhelming public support for stricter gun laws, many of the bills in Congress still remain in limbo - including one bipartisan measure with 69 co-sponsors that would strengthen a national background check for gun ownership.

“Politicians are petrified by the National Rifle Association,” Democratic Senator Dick Durbin of Illinois said Wednesday, sparking applause from a packed crowd that included protesters with signs lambasting the NRA.

Republican lawmakers on Wednesday were particularly critical of the FBI, as well as Florida officials, for not acting on tips or ensuring that Cruz received treatment for mental illness.

“At all levels, law enforcement must explain what went wrong,” Grassley said.

Bowdich said some preliminary findings and recommendations have been issued since the incident.

It was still not clear how the call taker at the FBI presented the Cruz tip to her supervisor before it was dropped, but the process will be improved going forward, Bowdich said.