The FBI can't figure out how to unlock the Texas church shooter's iPhone, and Apple has offered help (AAPL)

Another battle is brewing between FBI and Apple.

Apple CEO Tim Cook  (Getty/Justin Sullivan)

• The FBI says it can't access data on a phone used by Devin Patrick Kelley, the gunman who killed 26 people on Sunday at a rural Texas church.
• Apple said that it contacted the FBI but it has not yet received a request for technical assistance.

Another fight between Apple and the FBI is brewing, this time over an iPhone reportedly used by Devin Patrick Kelly, the man who went on a shooting rampage on Sunday killing 26 people at a church in Sutherland Springs, Texas.

In a press conference on Tuesday, the FBI said that it hadn't been able to access data on a phone used by the gunman. The Washington Post identified the phone as an iPhone.

"They're in the process of looking at the phone," Christopher Combs, the special agent leading the investigation into the shooting, told reporters on Tuesday. "Unfortunately, at this time, we are unable to get into that phone."

Combs' comments suggest that critical clues to Kelley's motivations or potential co-conspirators remain inaccessible on his device without knowing the password.

Apple told Business Insider that it reached out to the FBI after it saw the press conference on Tuesday.

"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," an Apple spokesperson said in a statement.

"We work with law enforcement every day. We offer training to thousands of agents so they understand our devices and how they can quickly request information from Apple," it continued.

The fingerprint sensor might still have been able to unlock the phone after Kelley's death

null  (Flickr/Kārlis Dambrāns)

The Apple spokesperson went on to confirm that law enforcement had not yet asked for any help from Apple accessing data off of Kelley's phone.

The implication is that had law enforcement contacted Apple sooner, it would have received tips and guidance that could have helped it preserve access to the data on Kelley's phone.

For example, as a security measure, the fingerprint sensor on iPhones won't work if the user hasn't used it in the last 48 hours. That suggests that for the two days after the rampage and after Kelley's death, but before the press conference, law enforcement could have used Kelley's actual finger or a copy of his fingerprint to access his phone.

Echoes of the San Bernardino showdown

The episode mirrors a fraught situation in 2016 when Apple and the FBI publicly clashed over access to an iPhone used by Syed Farook, a terrorist associated with an attack in San Bernardino.

At the time, Apple went public to fight a court ruling that ordered it to assist the FBI in bypassing critical security features on the device. But the FBI later announced that it was able to access the data on its own and dropped the court fight.

FBI officials have called for companies like Apple to build "back doors" into their technology — special ways for law enforcement to read messages and other data off of commercial smartphones.

A spokesperson for the FBI did not immediately return a request for comment outside of business hours.