Berlin, Germany (CNN) Murders happen in Berlin. They're not common -- the crime rate in Germany is currently at its lowest level in more than 25 years -- but as with all major cities, the occasional violent killing is all but inevitable.

What's far less common is for them to occur at noon, in the city center. And what's truly unprecedented is when the target is a former Chechen fighter, and the suspect an alleged Russian government hitman.

But that's exactly what happened on August 23.

Zelimkhan Khangoshvili, a 40-year-old Georgian citizen of Chechen descent, was on his way to midday prayers at a mosque in the Moabit district of downtown Berlin.

A man following him on an electric bicycle approached and shot him at close range twice in the head and once in the shoulder. Khangoshvili died instantly; his suspected killer was apprehended and remains in police custody.

If the alleged assassin was trying to be discreet, it's fair to say he failed. Two teenagers saw him throwing a handgun, wig and bike into the River Spree, setting off a murder mystery that has gripped the country and raised uncomfortable questions about Germany's complex relationship with Russia.

The suspect, who was carrying a Russian passport, was arrested within hours. But more than two months later, the case is still in limbo: the suspect won't talk, the Kremlin denies involvement, and Germany refuses to point the finger at Moscow without definitive evidence.

The murder has also cast a dark shadow over the tens of thousands of other Chechen migrants living in Europe. Vulnerable to deportation, and rising anti-migrant sentiment, they say they're closely watching Germany's response to the incident.

'We were in shock'

Khangoshvili had long been a wanted man. His participation in the Second Chechen War, where he fought alongside fellow Chechen insurgents against Russian federal forces, earned him deep enmity among sections of Russia's armed forces.

Despite leaving the resistance movement in around 2005, he could not shake off his past so lightly.

Numerous assassination attempts dogged him and his young family over the years as they sought refuge across Europe, finally coming to Germany in 2016 in the hope of finding a safe haven at last.

They could not have been more wrong.

Zelimkhan Khangoshvili

Khangoshvili applied for asylum three times but was rejected at each, according to Mansur Sadulaev, head of the Chechen-focused human rights advocacy group Vayfond in Sweden. Both Germany's immigration authority and the prosecutor in the case declined to confirm the number of applications Khangoshvili submitted.

"All his requests were ignored," he said, despite the previous assassination threats and his respectable family status. Khangoshvili's wife at the time, Manana Tsatieva, was previously a doctor at a leading private hospital in the Georgian capital, Tbilisi.

The final successful attempt on Khangoshvili's life, when it came, was still unexpected for Europe's Chechen community.

"We were in shock," said Sadulaev. "This had only happened once before, with [Umar] Israilov," he said, referring to the former Chechen rebel who was killed in Vienna in 2009. Austrian investigators believe the Chechen government was involved in the killing.

"No one expected that would be repeated," said Sadulaev. "The first time could have been a mistake, but the second time was a message. A very clear one."

A wanted man

Khangoshvili, who came from Georgia's Pankisi Valley -- a remote mountainous region on the border with Chechnya, in the North Caucasus -- grew up surrounded by war.

The valley was a place of refuge for thousands of civilians fleeing the Second Chechen War, which raged almost a decade, beginning in 1999. Among them were Chechens who had fought against the Russian troops.

Khangoshvili, an ethnic Chechen Georgian national, first began fighting against the Russian forces in 2001, his ex-wife Tsatiev told CNN.

"To join the forces who were fighting for an independent country -- it was completely normal," said Tsatieva, a small woman, elegantly dressed in a flowing skirt and headscarf, who moved to Germany with Khangoshvili and their four children.

''At that time, it was the best thing you can do for your country."

A police diver searches for evidence in the River Spree, close to where Khangoshvili was murdered.

In the late 2000s, Khangoshvili settled in the Georgian capital, Tbilisi. It was then that the assassination attempts began.

The first of these was in 2009, according to Aleksandre Kvakhadze, a research fellow at the Georgian Foundation for Strategic and International Studies, who first met Khangoshvili around this time; it was the start of a long friendship.

"A group tried to poison him, but it didn't work," Kvakhadze said, adding that Georgian security services found the group was linked to Russian intelligence and Chechen leader Ramzan Kadyrov.

Kadyrov is a former warlord known for his brutality -- and for his allegiance to Russian President Vladimir Putin.

In the group's eyes, it would have been bad enough that Khangoshvili had fought in Chechnya.

But he earned further Russian enmity by organizing a group of volunteers -- "about 200" of them, according to Kvakhadze -- from his native Pankisi Valley to fight invading Russian forces during the 2008 Russia-Georgia War.

The volunteers did not have the chance to deploy alongside Georgian regulars, according to Kvakhadze. But they nonetheless planned to aid in the defense of the capital, if it came to that.

Khangoshvili's contacts with former comrades came in handy in August 2012, when a group of roughly 20 Chechen and Dagestani militants were cornered by Georgian security forces on the border with Russia.

Officials with then-president Mikheil Saakashvili's government brought in Khangoshvili to try and negotiate a peaceful solution. Hotter heads prevailed, and a firefight left around half of them dead, despite his efforts.

One day in 2015, Khangoshvili was walking to his car in Tbilisi's Saburtalo neighborhood. Suddenly, gunfire erupted behind him, striking him four times in the arm and upper body. He slumped against the vehicle and managed to call an ambulance.

"It's a miracle he survived," says Kvakhadze, who visited Khangoshvili in the hospital shortly after the attack.

'He had to leave Georgia to stay alive'

There were suspicious inconsistencies in the investigation that followed, according to Kvakhadze. The new Georgian authorities, who in 2013 replaced the Saakashvili team Khangoshvili had worked with, claimed there was no camera footage of the area of the attack -- despite its location in a central neighborhood of Tbilisi.

The attack was treated as a petty criminal incident, rather than a potentially politically motivated event. Khangoshvili's right to carry a firearm for self-defense had been revoked in the months leading up to the assassination attempt, though no explanation was given by authorities. No suspect was ever named or caught.

Khangoshvili was sure who was behind the attack. "He had no doubt it was Russian intelligence," said Kvakhadze. "He suspected that Georgian security services allowed them into the country to conduct the operation."

Russia has denied any connection to Khangoshvili's killing. "This case has nothing to do with the Russian state, with official bodies," Kremlin spokesperson Dmitry Peskov said in response to media reports about the case, according to Russian state news agency TASS. "I categorically reject any connection between this murder and official Russia."

Even when Khangoshvili heard from informers that there would be another attempt on his life, "we had no protection for him," said Tsatieva.

"We had 10 to 15 friends protecting him around the clock for him to stay alive," she added. "But we could not go on like this. He simply had to leave Georgia to stay alive.''

Khangoshvili took refuge in Odessa, Ukraine, in 2015. Again, they were warned by informants that he would be killed if he returned home, said Tsatieva.

"We wanted to build a bright future in Germany," she said. "To have a safer life and to be together again as a family.''

It wasn't to be.

Shortly after arriving in Germany in 2016, Tsatieva learned that Khangoshvili had another wife in Ukraine who was pregnant. Tsatieva and Khangoshvili -- who had been married for two decades -- split and had minimal contact from that point on.

Hopes dashed

Khangoshvili's life in Germany initially seemed safer, but it was no less difficult: his asylum applications were rejected three times.

Now his murder, and the emerging evidence that alleges links to Russian security services, have prompted many to ask why the German government has been uncharacteristically quiet on the matter.

Since the killing, no German authorities have contacted Khangoshvili's family to "convey condolences or apologize for the lack of protection," said Tsatieva.

"I don't find it normal that a person is shot -- a person is murdered, killed by a person from another country," said ex-wife Tsatieva. "A person who was asking for protection -- and was denied protection in Germany."

"I had hoped for some human reaction," she added, choking back tears.

Germany's Federal Office for Migration and Refugees, along with the Attorney General's office, declined to comment, telling CNN that they do not discuss individual cases.

So far, the German government's reaction to the killing has been muted. When questioned about it by journalists during a press briefing in late September, Chancellor Angela Merkel's spokesman, Steffen Seibert, said Germany had "a great interest in a comprehensive investigation of this crime."

For Chechen rights group spokesman Sadulaev, it's a sadly predictable continuation of the existing neglect of Europe's tens of thousands of Chechen refugees.

"I can't say that I'm surprised," he said of Germany's response. "Russia is a great power, and Germany is not interested in harming relations over this. Chechens are just an inconvenience."

Chechen migrants in Germany and elsewhere in the European Union face myriad problems. They often have extreme difficulty securing status documents, with most only possessing a "Duldung," a "temporary suspension of deportation" certificate that means they are obliged to leave the country at some point in the indeterminate future.

A Chechen family seeking asylum in Germany walk into their temporary home in Letschin.

This means they have no legal right to work, and their only housing options are usually overcrowded migrant centers. Lacking other opportunities, some turn to criminal activity and gangs.

German political trends and rising anti-migrant sentiment have played a role in Berlin's reaction, said Guido Steinberg, a senior associate with the German Institute for International and Security Affairs.

"Resistance to asylum seekers has grown sharply since 2016, and Chechens do not have the best reputation," he said. There is also a "very strong pro-Russian trend in German politics," including those who will protest measures against Russia "no matter the proof."

There are other complicating factors. "There is a widespread belief that it is next to impossible to truly integrate Chechens into German society," said Steinberg.

While he is sympathetic, he notes some hard truths, including that Chechens "often have low levels of German, even after many years," and that "a relatively high number of [Chechen] jihadis" left to fight for ISIS and other groups in Syria.

Steinberg is meanwhile sure that if Russia is found to have been behind Khangoshvili's killing, a harsher response is likely. "The incident is being taken very seriously, but security services are waiting for a fool proof conclusion that it was a Russian operation," he said. "If they reach this conclusion, they are convinced they have to act."

Scant comfort for family

This will come as little comfort to Khangoshvili's relatives.

His brother, Zurab, lives in Sweden with his two children. Shortly after the murder, he traveled to Germany and approached authorities there, looking for answers. In their latest update earlier this month, German officials told Zurab that the investigation was ongoing and that the case would go to court in the next few months.

Back in Sweden, Zurab's own children are facing deportation to Georgia. Zurab said he appealed to Swedish courts following the death of his brother, citing fears for the safety of his children. But he said the family was told that since his sons were nephews of Khangoshvili, they were considered "distant relatives" and as such were not "under any danger."

The family sees it very differently. "We gave them so many documents, so much proof, that their lives will not be safe [there]," said rights group spokesman Sadulaev, who is personally involved in the case. "They ignored it. Even Khangoshvili's death was not a good enough reason for his brother to receive asylum."

CNN contacted Swedish authorities for comment but had not received a reply at time of publishing.

Zurab last spoke with his brother on the phone the day before he was murdered. "We were talking about sending my children to Germany where they could file for asylum and what he could do as an uncle to help his nephews.''

Hours later, his brother was dead. Two months on, the suspect "continues to exercise his right to remain silent," according to Martin Steltner, spokesman for the Berlin Prosecutor's office.

The suspect can be held in custody for six months, said Steltner. After that, if there is insufficient evidence against him, he will be a free man. However investigations are ongoing, Steltner added, and the evidence is promising.

Meanwhile, the ongoing silence -- from the suspect as well as Germany -- has become deafening for Khangoshvili's family and thousands more Chechen migrants across Europe.