POSSIBLE ACCOMPLICE SOUGHT IN ARIZONA…. Jared Lee Loughner, the 22-year-old suspect in yesterday’s massacre in Tucson, was tackled by people on the scene and quickly taken into custody. Late yesterday, however, we learned that law enforcement officials are looking for another man who may have been involved with the shootings.

[Loughner’s] motivation was not immediately known, but Pima County Sheriff Clarence Dupnik described him as mentally unstable and possibly acting with an accomplice. He said in addition to the six deaths, 13 people were wounded in the melee. Dupnik said the rampage ended only after two people tackled the gunman.

Investigators said they were looking for an accomplice, believed to be in his 50s, who may have assisted in the attack.

Dupnik said authorities have pictures indicating the existence of a second person aiding in the attack.

In the meantime, the Pima County Sheriff’s office released the names of the six people killed in the attack. In alphabetical order: Christina-Taylor Green, just 9 years old; Dorthy Murray, 76; U.S. District Court Judge John Roll, 63; Phyllis Schneck, 79; the Rev. Dorwin Stoddard, 76; and Gabriel Zimmerman, the 30-year-old director of community outreach for Rep. Gabrielle Giffords (D).

Giffords was shot in the head, but by last night, reports indicated that she’d regained consciousness and recognized her husband. There were 12 others injured.

According to an account from a Giffords spokesperson, the gunman fired first at the congresswoman, before shooting indiscriminately at others nearby.

If an accomplice was involved, it would seem to change the nature of the incident, away from just a lone nut with a handgun, but we’ll have to wait for additional information.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.