It remains unclear, however, whether the phone will provide more clues in the deadliest terrorist attack on U.S. soil since 9/11.
Now that the FBI has unlocked the iPhone, do we know what officials found on it?
No. Officials have not provided any details about the contents of the phone.
The FBI sought to unlock the iPhone 5c used by one of the San Bernardino shooters because they believe the encrypted data may answer questions about whether they had assistance.
They thought the phone might also provide information about where they went before and after they killed 14 people during a holiday party on Dec. 2.
Officials recovered Syed Farook’s iPhone from a black Lexus parked outside his Redlands home.
Is it possible there were others involved in the attack?
At this point, there is no evidence of that. The FBI has said the couple appear to have acted alone. Officials said they were "self radicalized" and had sympathies for Islamic terrorist groups. But they said the attack was not part of a larger plot.
A friend of Farook's was charged with providing guns used in the attack. But authorities said he was not involved in the attack itself. In fact, surveillance video shows him at work at the time.
How about talk on the day of the attack about a third shooter?
Officials say there was no third shooter.
But the early reports of a possible third shooter — a source of worry for first responders racing to the scene — continue to bedevil authorities.
A handful of victims interviewed by police still maintain they saw a third attacker. The father of one victim raised the possibility while weighing in on the legal dispute over investigators' attempts to gain access to Farook's work iPhone.
Why was it so hard to get into Farook's iPhone?
The FBI was unable to access the phone because it did not have the password. Farook had not backed up the iPhone to iCloud data storage for a month and a half, so some data was only available from the iPhone itself.
The phone is owned by San Bernardino County Department of Public Health, where Farook was a health inspector, which consented to the search. But federal agents could open it because it uses an IOS 9 operating system with a two-stage authentication.