ALVARADO — A female clerk at an Alvarado truck stop was shot and seriously injured during a robbery attempt early Wednesday.

Police said the 52-year-old employee at the Shell Travel Center at Interstate 35W and Highway 67 was alone in the store mopping the floor when the gunman entered at 1:35 a.m.

"He walks in, comes up behind her and shoots her in the head," said Alvarado police Chief John Allen. "Very calm; very cool."

The gunman then went over to a cash register — tried and failed to open it — and left the premises empty-handed.

A customer found the victim a few minutes later. She was in grave condition at noon Wednesday at John Peter Smith Hospital in Fort Worth.

The gunman was described as a Hispanic male wearing a dark hooded sweatshirt and gloves. He was estimated to be about 5'-5" tall. He was carrying a small caliber handgun.

A surveillance tape could provide additional clues to the identity of the holdup man. The FBI was helping Alvarado police improve the quality of that recording for distribution.

E-mail jdouglas@wfaa.com