After the FBI said it was dealing with a phone it couldn't open, Apple reached out to the bureau to learn whether the phone was an iPhone and whether the FBI was seeking assistance. An FBI official responded late Tuesday, saying that it was an iPhone but that the agency was not asking anything of the company at this point. That's because experts at the FBI's lab in Quantico, Va., are trying to determine if there are other methods, such as cloud storage or a linked laptop, that would provide access to the phone's data, these people said. They said that process could take weeks.

If the FBI and Apple had talked to each other in the first two days after the attack, it's possible the device might already be open. That time frame may have been critical because Apple's iPhone "Touch ID" — which uses a fingerprint to unlock the device — stops working after 48 hours. It wasn't immediately clear whether the gunman had activated Touch ID on his phone, but more than 80 percent of iPhone owners do use that feature. If the bureau had consulted the company, Apple engineers would likely have told the bureau to take steps such as putting the dead gunman's finger to the phone to see if doing so would unlock it. It was unclear whether the FBI tried to use the dead man's finger to open the device in the first two days.

In a statement, Apple said: "Our team immediately reached out to the FBI after learning from their press conference on Tuesday that investigators were trying to access a mobile phone. We offered assistance and said we would expedite our response to any legal process they send us."