Piggee, 24, also pleaded guilty to causing a fire on the same day at a Wal-Mart on Antelope Road.
Piggee is scheduled to be sentenced in May on two counts of arson.
He faces a maximum sentence of 20-years for each count. But Assistant U.S. Attorney Steve Lapham says under a plea agreement, the Department of Justice is recommending only 10 years.
"That was kind of in recognition of the fact that the kid is young, he did a stupid thing which had tragic consequences of course, but it was done out of a malevolent motive or a profit motive like we usually see in arson cases."
Piggee's attorney says his client is remorseful and receiving
treatment for mental problems in jail.