The second official described what in effect appears to be a drug robbery.

“So Tamerlan says they have dope, they rip them off. Tamerlan says, ‘They can identify me, so let’s kill them.’ And they kill them,” the official said.

Image Ibragim Todashev Credit... Orange County Sheriff's Office

If Mr. Tsarnaev was involved, then the murders may shed light on the crucial question of what may have turned him violent and unstable, and whether that was before he traveled to his homeland in the North Caucasus region of Russia last year.

The recent focus on Mr. Tsarnaev’s possible involvement in the Waltham murders has also raised questions about whether authorities in Massachusetts missed an opportunity to thwart the marathon bombings by not adequately pursuing Mr. Tsarnaev as a murder suspect.

There was no indication on Wednesday why Mr. Todashev — who, like the Tsarnaevs, was an ethnic Chechen — would have implicated himself and Mr. Tsarnaev in the murders. Investigators, who are seeking to determine how Mr. Tsarnaev made money, have been looking into whether Mr. Todashev and Mr. Tsarnaev were drug dealers, one of the law enforcement officials said.

Mr. Todashev had not signed a written statement about the Waltham murders before he was fatally shot. “He had only said it orally but had not signed anything,” said the first official. “But that was where it appeared to be heading.”

The shooting occurred in a sprawling condominium complex in Orlando, less than a mile from an entrance to Universal Studios, where many of the residents work. On Wednesday, several streets in the complex were blocked off by federal and local law enforcement officials.

The law enforcement official said that the authorities had spoken to Mr. Todashev at least twice since the April 15 bombings in Boston, which killed three people and injured more than 200.