It's that time of year, the time when teams hire out open-top buses and parade around city centres shouting about how great they are. PSG fans celebrated extra hard and the riot police were called.
To me this just looks like a group of guys enjoying a game of ultimate fireball. PSG fans were delighted to see their team lift the league trophy and showed their support the traditional way with fireworks and flares. Apparently the police weren't happy with the players milking the applause and taking too long to say their thanks yous - so they quickly tried to move on the victory parade. All pissed off that the celebrations were finished so early, the fans threw stones and "objects" at the police, who responded with tear gas.
The evenings festivities were slowed up by an hour or so, but they got back on track and all the players partied with boats and hos. Everybody had a great old time and they all lived happily ever after. Except the 28 people who died and 100s who were injured.
(nobody died, although Zlatan roundhouse-kicked Leonardo in the face)