I largely agree that they likely gain little from accessing the phone (though they may further understand motive/sources of radicalisation from what he was look

I largely agree that they likely gain little from accessing the phone (though they may further understand motive/sources of radicalisation from what he was looking at before the shooting), but it would seem negligent not to check if they have access to it. It doesn't seem to warrant spending significant resources finding a way into it, though (unless they have reason to suspect the involvement of a third-party), or justify calling for a backdoor.