NEWARK -- Officers arrested an 18-year-old man Friday in connection with the brutal robbery and assault of a 70-year-old woman in front of a Walmart store the previous week, a Fremont Police Department spokeswoman said.

Geneva Bosques said Newark resident Alberto Solano was arrested in Newark about 1:20 p.m. by both Fremont and Newark police after an off-duty police officer who saw footage released to the media called in with a tip, saying he recognized Solano from previous interactions.

Bosques did not say exactly where Solano was arrested or what charges he might face.

A young woman who was with Solano at the time of the robbery has not been located.

The robbery took place Oct. 4 in front of the store at 44009 Osgood Road in Fremont.

The woman was leaving the store with her family when she was approached from behind by Solano, who grabbed her gold chain necklace, police said. The woman attempted to hold onto her necklace as she was pulled from behind, and a brief struggle ensued before Solano slammed the senior to the ground.

A still-unidentified female, who was with Solano at the time of the incident, ran to a nearby vehicle, where she waited for him. The car was described as a silver or gray four-door Hyundai with tinted rear windows.

The woman was taken to a hospital with a serious injury that required surgery and hospitalization, according to police.

Anyone with information about the incidents is asked to contact Fremont police at fremontpolice@fremont.gov or to call the Investigative Unit at 510-790-6900. Anonymous tips can be left at www.fremontpolice.org/tip.

Staff writers Kristin J. Bender and Natalie Alund contributed to this report. Contact Katie Nelson at knelson@bayareanewsgroup.com and follow her at Twitter.com/katienelson210.