How to tell difference between flirting or being friendly?

My state has people who pump our gas for us. This guy(jay) comes up to me said "i like your shirt" he goes back to the cash register in front of my car basically. Came outside of it and started to talk about music. Asked if I went to warped tour. Told me his coworkers tell him to turn the devil music down. I go back a few days later and he comes up he starts talking to his coworker shouting basically saying "to take my shift for me work double. I have to go on a fire truck when it's raining" another coworker walks away and jay shouts at him saying "I love youuuu. Why don't you love me?!?" He was being sarcastic you could hear it in his voice. Neither of his coworkers even said anything to him