"There was nothing wrong when I dropped her off at school," her mother told the Houston Chronicle. "The only thing that threw me off was she told me she loved me when she got out of the car."
At some point she left school then walked to a bus station where she persuaded someone to buy a bus ticket to get to the Mexican border.
Security footage from a bus station shows Ashlee wearing jeans, a blue shirt, jacket and brown boots getting ready to board a bus bound for Laredo.
Officials believe she got off a bus in the Laredo area to cross the border into Mexico.
"Our efforts are focusing on the Laredo area where we've had some reports of possible sightings," Harris County Sheriff’s Office spokesman Jason Spencer, told the Chronicle. "We feel confident right now that our best leads are in Laredo."
Attention Laredo-area news media. Please spread the word that missing teen Ashlee Hattermann, 13, may be in your area and in danger. She's 5'7", 110 lbs, with blue eyes and brown hair. Might be wearing glasses. Call 713-755-7427 w/info. @lmtnews@kgns@laredofox#hounewspic.twitter.com/alPgTArpSV
The FBI and Department of Homeland Security are helping investigate, according to the Chronicle.
"We are working with Mexican authorities in an effort to locate her in Mexico, but we are also seeking any information anyone in the United States may have which may help us find her," FBI spokeswoman Michelle Lee told the Chronicle.
FBI San Antonio Laredo office joined in investigation of missing 13-year-old Ashlee Hattermann, last seen in Katy, TX on Friday, 12/1. Ashlee traveled to Laredo, TX & crossed into Mexico late Friday. She is 5'7", 130lbs, long brown hair, blue eyes. Call FBI 210-225-6741 pic.twitter.com/VruKKeNkBd
Her parents found lurid messages a year ago between her and a 29-year-old man from Mexico, according to KHOU. They took away her phone and gave it to the Sheriff’s Office cyber crimes division. Somehow Ashlee got another phone and continued communicating with the man, her mother said.
“We found a note in her room,” Ashlee’s father Keith Hattermann told KHOU. “She calls the guy ‘daddy’ and herself ‘baby girl.’ (The note read) ‘Daddy owns my body and my soul,' over and over and over again down this sheet of paper.”
“We just feel helpless,” he said. “We just want her back. We just want her safe.”