At first we saw just one snake, but Larry said he saw two slither into a crack under the pavement on one of the building. Fox snakes are nonvenomous and constrict their prey (mostly mice, some small birds and eggs). They will coil up, vibrate their tail making a rattling sound and strike out when threatened. This defense probably developed to keep predators away since they could be mistaken for a rattlesnake. However, humans who don't know and mistake them for rattlers will kill them. Interesting that a behavior that evolved to protect them, now is more likely to get them killed.
Below is an 8 second video of the fox snake giving its fake rattle: