Store surveillance shows suspect w/2 qt bottle of Kingsford lighter fluid police believe he lifted from garden dept. pic.twitter.com/HqmiQZPIIt — Laura Anthony (@LauraAnthony7) October 13, 2015

Pile of charred #Halloween costumes outside San Leandro #Walmart where man doused them with lighter fluid and lit. pic.twitter.com/UpFa06X1ja — Laura Anthony (@LauraAnthony7) October 13, 2015

SAN LEANDRO, Calif. (KGO) -- Smoke and flames cleared out a San Leandro Walmart store Tuesday. It was all started by an arsonist who walked into the store, sprayed lighter fluid all over and lit the place on fire.Investigators are interviewing the suspect and they are trying to figure out why he did it. Loss prevention operators said they saw the man pushing a cart around the store early in the morning with a leaking bottle of lighter fluid. A few hours later, he allegedly lit the place on fire.Paul Miller says he shot a video shortly after a man walked into the San Leandro Walmart on Hesperian Boulevard and set the Halloween costume aisle on fire."My biggest concern at the time was to make sure that all the families were out," Miller said. "It looks like some kids were there as their parents were helping them shop for Halloween items."Mario Lopez, a witness, says it was about 1:30 in the afternoon. He was waiting at the pharmacy for his prescription."Just before she handed me the prescription she said, 'Sorry, fire. Get our of here.' So everybody scrammed. And we went out of the garden area, and people were flocking out like you wouldn't believe."Police say a 40-year old Oakland man who lit the fire was in the garden center earlier. That's where he picked up a bottle of charcoal lighter fluid and began squirting it around the store."If it weren't for the security people, if it weren't for the store employees inside that put this fire out right away, this could have been much more tragic," said San Leandro police Lt. Robert McManus.He only lit one aisle on fire before a Walmart employee said he and a security guard tackled the man and held him until police arrived."It's was scary. Everyone was freaking out. It's like, oh my goodness, what is going on here?" said witness Naomi Santiago."You can't even shop without worrying about somebody doing something insane," Lopez said.In spite of the chaos, witnesses say Walmart employees calmly led customers out of the store.