Though Chris Brown was booked on a charge of criminal threats after allegedly beating his girlfriend, Rihanna, E! reports that the singer is being investigated for a multitude of other felonies:

At the request of the Los Angeles District Attorney's Office, the R&B star is being investigated for a variety of felonies, including domestic violence, assault resulting in great bodily injury and—based on specific allegations made by Rihanna—even attempted murder, a source close to the L.A. Police Department's investigation tells E! News.

But as they build their case, the source says, prosecutors fear that making any serious felony charges stick could prove difficult in a case where there are no direct witnesses other than Rihanna and Brown.

Reached for response, a mercifully flack-muzzled Terrence Howard responded, "Mmmmf mmffffffgh." Developing...