Croats and Portuguese riot in Germany

I saw in the Guardian:

German authorities have expressed shock over a rampage of an “unprecedented scale” in the centre of Stuttgart, where hundreds of partygoers ran riot overnight and into Sunday, breaking shop windows, plundering and attacking police.

Two dozen people, half of them German nationals, were provisionally arrested and police reported 19 officers hurt. “They were unbelievable scenes that have left me speechless. In my 46 years of police service, I have never experienced this,” said the Stuttgart police chief, Franz Lutz.
Tensions built up shortly after midnight when officers carried out checks on a 17-year-old German man suspected of using drugs, said Stuttgart’s deputy police chief, Thomas Berger.

...At the height of the clashes, some 400 to 500 people joined in the battle against police officers and rescue workers.

As officers pushed back against the crowd, they broke up into small groups, carrying on their rampage around the city centre, breaking shop windows and looting stores along nearby Königstraße, a major shopping street.

Half the people arrested were German nationals and, asked about the nationalities of the 12 non-Germans who were detailed, the police said they came from a range of countries, from Croatia and Portugal to Afghanistan and Somalia. 

But are the Stuttgart police and the Guardian telling us the whole story?

Elsewhere on the net I found the AfD blaming the “civil war” in Stuttgart on the massive influx of migrants to the city, noting that 

It is no coincidence that it hit a city with a 44 per cent migrant population. Without a political paradigm shift, such scenes will repeat themselves in Stuttgart and in other German cities. What we need is consistently controlled immigration, more police and a crackdown on the judiciary against such criminals. 

My suspicion is that ethnic Germans, Croats and Portuguese might not be the majority of the rioters.

Clues are found in the Deutsche Welle account. DW spoke to a bystander called Yussef. 

When asked where the "rage" came from, Yussef explains that many of the young people involved in the clashes, particularly people of color, feel they're too often regarded as suspects by police.

The tensions have become particularly raw in light of the protests against police brutality that launched in the United States.