"You should immediately start thinking that that child needs to get out of that vehicle," said Tempe Police Lt. Mike Pooley.
Spotting a child left behind in a car can be a matter of life and death and Pooley said if people see a kid left inside a vehicle they need to act.
He said to look around to see if the owner might be in sight, check and see if the doors are unlocked, and call 9-1-1 immediately. Beyond that, if the child looks in distress, people need to do whatever they can, Pooley said.
"If there's nobody around and that child looks like they are sweating profusely, if they're crying immensely, if they're not moving, these are things that should be red flags to anybody that's walking by that would see a child like this," he said. "You need to do everything you can to get that child out of the vehicle."
Pooley said a child's life is too important to ignore and the temperatures inside cars can quickly reach lethal levels even if it's not excessively hot outside.
"If your intent and you're working in manner that you believe that child is in duress and that that child needs to get some fresh air (and) that that child is about to die," he said. "Then by all means do what you have to to get in that vehicle."
Pooley said at the very least people should always call police if they feel something might be amiss or see a child that might be in distress.
"We're human; sometimes we see something that may not be the right thing to do, but you can never go wrong calling the police department (or) calling the authorities," he said. "We would rather get out there to make sure everything is fine that a child's not in any danger than for somebody to walk by and ignore a gut feeling or to ignore a feeling that they should do something."