They've also released a 911 call and announced an increased reward in the case.
Zuheily Rosado was working the evening shift at the Mobil Gas Station on East State Route 100 at 10:09 p.m. when the man went in and shot her, then left Flagler County deputies said.
They said a customer found the body of Rosado on the floor behind the counter, dead of a gunshot wound to the head.
Investigators said they have been unable to establish a clear motive for the killing.
Rosado was a 32-year-old mother of six.
Deputies said the killer is seen on video entering the store. He was described as a light-skinned man, about 5 feet 10 inches tall, wearing blue jean pants and a dark T-shirt.
Surveillance video of Palm Coast Mobil store shooting
The man is seen in the video pulling his shirt up over his face and is then seen fleeing the store moments later and heading west toward the entrance ramp to Interstate 95.
"He doesn't take anything. He doesn't intimidate. He goes directly in and shoots the victim and he runs away," said Channel 4's Crime Analyst, Ken Jefferson. "It's difficult for investigators simply because they don't have a lot to go on. They're going to be interviewing friends and family… anyone who had any knowledge of the victim that maybe they can get a clue or hint as to how would want to do this kind of thing."
Rosado's family is also in disbelief.
"I just want my mom back," Rosado's oldest daughter, Teysha Silva, told Channel 4's Hailey Winslow.
An account has been set up at Wells Fargo under the name of Zuheily Rosado Memorial Fund. Donations are being accepted at any Wells Fargo branch. The family says they are in dire need of money by 3 p.m. Tuesday to pay for funeral expenses. Donations can also be sent to the Justice Coalition, 1925 Lane Avenue South, Suite #1 32210 in Zuheily Rosado's name.
The reward for information leading to the killer's arrest has been increased by Crime Stoppers of Northeast Florida to up to $5,000.
"This is how this kind of case is solved. Someone will come forward, a lot of times they'll want to remain anonymous, and they'll give a tip to police as to who they think this person may be based on a previous conversation, based on them knowing the victim, or the suspect, or a combination of the two," said Jefferson.
Anyone with information about the killing is asked to call Flagler County Sheriff's Office Detective Mark Moy at 386-586-4801 or Crime Stoppers at 888-277-TIPS. Tipsters can text information by texting "tip231" plus their message to CRIMES (274637). Tipsters to Crime Stoppers can remain anonymous and could qualify for a reward of up to $5,000.