Advice on dealing with a threatening creep?

Our church group (consisting of about 6 men, 6 women, and several young people & children) was at an outdoor public event the other day, and had a creepy interaction with a guy. He's a young clean-cut looking guy, no obvious drinking/drugs/mental impairment. We've seen him before at a few other public events, and he apparently hates what we stand for, because he has made some general threats and taunts before. However, this time he got more specific.

A lady that was not with our group but was talking to us heard him harrassing us verbally, and she walked over to talk to him - she basically I guess told him to hush up. She hurried back, saying that he had told her "I'll kill you and your whole family." I don't know her very well, so I didn't really know whether to believe her or if she misunderstood him or provoked him or what. She saw a police officer nearby and told him, and the creep came over and said flat out, "She's a liar. She's nuts. I never said any such thing." The cop just told him to go over to the other side of the street, and that was that.

However, another lady who was in our group later said that he came up to her after that, and in a low voice said some very disgusting things - not direct threats but very creepy stuff about rape and necrophilia.

Then for the next hour or so that we were there, he and his equally creepy buddy stayed where they could watch us, and casually trailed behind us when we moved up the street as a group. Needless to say, we had alerted everyone in the group and the parents were keeping a close eye on the children. We deal with rough people all the time in our ministry, so we weren't overly intimidated, but cautious and watchful.

When we finally broke up and went to our respective cars, parked several blocks away, I was concerned he might follow one of the families, but as far as I know, he didn't. I was glad I had parked alongside another family so I didn't have to walk back alone.

There are only two of us in the group that carry. I sure felt a lot safer knowing I could protect myself if he did decide to follow and start something.

So here's the thing: we will very likely run into him again. We don't know his name or anything about him. There is a remote possibility that he works for the city or for an agency associated with the city because of where & how we first encountered him months ago. I had my camera with me and did get him on film, but of course he didn't make any threats in my presence due to the camera.

Any thoughts or advice on this? Needless to say, we'll be on high alert next time we're out, and I carry all the time. But what do you do if there is no direct threat? I mean, a guy approaching a woman and threatening to rape her is one thing. But a guy standing next to a woman and just talking about how much he enjoys raping women - to me that's a threat, but how does that pan out as a reportable offense (especially without an ID for the guy) or a self-defense issue?

LibertyGal