JOHN LARSON: Joining me now by Skype from Paris is Andrew Callus of Reuters. Andrew, thanks so much for joining us.

First of all, you know, we are just hearing that, you know, the first gun jammed, the second one wasn't fully loaded. It sounds like an extraordinarily lucky situation.

ANDREW CALLUS, Reuters: It certainly does, yes. The three young American men who were involved in the — in the — in bringing the gunman down were giving a press conference a little while ago, and they said that it was quite clear he had no weapons training, two of those servicemen, so I guess they should know.

JOHN LARSON: What does that lead investigators to think about this gunman? Where was he from?

ANDREW CALLUS: He spent his adult life in a very poor, drug-, crime-ridden, unemployment type of suburb of Algeciras. So we know that about him.

A local community leader said he was a pretty ordinary young man who went — played football, who went fishing.

JOHN LARSON: Are there any actual ties being shown yet to any terrorist group?

ANDREW CALLUS: Not as yet. He was — so he was on a list of suspected Islamist militants. He basically had been thought to have had ties to — to some groups.

The boldest assertion we have seen is in a Belgian newspaper, which says he was linked to the group which was involved in a shooting in Brussels just a few days — a few days after the one in Paris in January.

JOHN LARSON: I read that he was on this S-list in France, where they are tracking, you know, people they are concerned about.

How many people are on these types of lists?

ANDREW CALLUS: The prime minister earlier this year said there were 3,000 on that S-list who were considered to be Islamist militants.

And of course, the problem is, until they actually do something that they could be arrested for, there's not very much anyone can do to actually stop them from moving around.

The countries that the train was traveling through, people travel across borders without passports, without security checks and so on. So these people can — can travel around.

JOHN LARSON: Ever since the first news of this arrived here in the United States, there's been questions about whether or not he actually — the gunman actually went to Syria. Any news on that?

ANDREW CALLUS: Sources within Spanish security services are saying he did go to Syria from France, not necessarily directly.

The French security services say that they know he traveled from Berlin to Istanbul on May the 10th of this year, or at least that he was in Berlin Airport on his way to Istanbul.

Now, Istanbul, in Turkey, that is a destination for a lot of would-be European jihadists wanting to go and join the fighting in Syria.

JOHN LARSON: Finally, any idea of whether or not they are going to have to change or ramp up security measures on the train?

ANDREW CALLUS: They are certainly talking about it.

It has been a few years now that people have said that these Thalys high-speed trains between — between the European countries are potentially vulnerable to an attack.

And here we have one. That is certainly going to be a debate over the coming weeks.

JOHN LARSON: Andrew Callus, from Reuters in Paris, thanks so much for joining us.

ANDREW CALLUS: My pleasure.