good bye US, hello mexico

so our adventure to mexico started off a little shaky. We drove 3.5 hrs through torrential rain and floods to get to the border town of Laredo. We parked and walked across this bridge (toll $.50). As we were walking into the toll gate, we heard sirens and a cop pulled this car over right next to us. As we go into the toll some guy started to scream "bomba" and next thing we knew they closed the toll and we were stuck on the bridge to mexico. All u could see is the sirens of firetrucks and cop cars on the US border. A mexican officer was yelling us to move and to run towards Mexico....