The federal courthouse in Alexandria. (Gerald Martineau/The Washington Post)

In the pre-dawn Wednesday, hundreds of federal agents and police officers waited on alert outside 20 homes in the Washington area for the clock to hit 6 a.m.

Once the hour arrived, law enforcement officers simultaneously shattered the morning quiet as they knocked down doors and tactical teams tossed flash-bang grenades in several homes to arrest targets of a months-long investigation into the activity of a gang and another armed group and gun and drug trafficking.

"All 20 houses got hit at the same time," said Special Agent in Charge Thomas L. Chittum III of the Bureau of Alcohol, Tobacco, Firearms and Explosives' Washington field office. "Those are some pretty tense moments while you are waiting for them all to check in."

Hundreds of pages of court filings detail how agents tracked drug packages between Virginia and California and did surveillance on men and women who are alleged to have moved drugs through the homes and businesses of a loose network of dealers. The stakes were so high for one suspected dealer that he chewed off his own fingerprint to keep investigators from using it to unlock his phone, court filings state.

More than a dozen targets of the takedown appeared in federal court in Alexandria on Monday and were held without bond.

The cases against dozens of defendants sprouted from information provided by a cooperating gang member named "Platinum," who told law enforcement that a Bloods-affiliated group was responsible for drug and firearm trafficking, killings, robberies and home invasions across Northern Virginia.

That top gang source and other confidential informants infiltrated the crew and used cash provided by law enforcement to buy large quantities of crack cocaine, cocaine, marijuana and firearms and, at times, wore recording devices to capture transactions from the spring until the fall.

The complex effort, dubbed Operation Tin Panda, targeted 50 people in response to a tide of bloodshed in Prince William County and to stop the gang's activity in other parts of the area. Authorities allege the activities have been linked to six killings and more than 20 shooting incidents, multiple home invasions and at least two carjackings.

Agents and officers seized more than 70 guns before Wednesday's raids and over 20 more Wednesday, in addition to thousands of dollars in cash and illicit drugs.

"These 100 guns off the streets, these particular targets off the streets, these trigger pullers off the streets, mean safer communities," Chittum said.

The killings connected to the investigation include an August double homicide in Lorton, Va., stemming from a dispute over the marijuana business; a shooting at a hotel in Alexandria in May; a 2015 slaying in the District; and a gang dispute in Fredericksburg this year, according to court documents and law enforcement.

Forty people were charged in federal court as part of the operation, along with another seven in Virginia state courts. While many of the accused have long felony records, some — including Tarvell Vandiver, identified as a high-ranking regional leader in the Imperial Gangsta Bloods gang — have none.

Platinum was not named in court documents, but he held a rank in the gang as "4-Star General" in charge of finances.

It was Platinum who named Vandiver as the local disciplinary officer and meeting organizer for the gang, according to court records, and he pointed to Vandiver's stepfather, Rashourn Niles, as a supplier of heroin, cocaine, marijuana and MDMA. Court records show Nasiru Carew was described as a main supplier of marijuana and THC gummies produced in California and shipped to a network of homes and other locations around Northern Virginia.

Investigators tracked parcels mailed by the U.S. Postal Service from the San Diego area, where officials say Carew had connections, and were flagged by postal inspectors when drugs were detected.

Platinum began cooperating after an arrest in Maryland on drug and gun charges, and he recorded dozens of drug buys and the distribution of illegal firearms, court filings show. He recorded gang meetings where Imperial Gangsta Bloods talked about smuggling guns to New York, the filings state.

In May, investigators followed a shipment to an auto repair shop in Fredericksburg, which led the Stafford County Sheriff's Office to arrest Robert Evans for conspiracy to distribute controlled substances, court document say. Authorities believe he had received packages of THC gummies and was selling them out of the shop.

While investigating the Imperial Gangsta Bloods, agents came across an unrelated armed group in Prince William County dealing large amounts of crystal meth, disproportionately to the D.C. gay community, and that group became part of the takedown, according to law enforcement officials.

Court files say that defendants used encrypted chat and video apps for conversations. The documents said that after Evans was arrested, he chewed off his own fingerprint in an attempt to keep law enforcement from using it to unlock his cellphone.

The filings show the alleged gang members were also flaunting guns and drugs on social media, which investigators used to track their activities and movements. Vandiver chatted online about selling crack, according to the court documents, while Carew directed the sale of THC gummies over Instagram. One felon was charged with illegal possession of a firearm after he posted a video of himself at a shooting range on Facebook.

And agents used addresses sent over social media to help them track packages sent from California.

Carew, Evans, Niles and Vandiver were those held without bond Monday.

Chittum said investigators faced two major challenges during the extended operation: taking targets off the streets as the case unfolded and coordinating the logistics of using more than 300 law enforcement officers and support staff to safely strike 20 homes at once.

"The operation on Wednesday went as well as any operation I have seen at that scale," Chittum said.

ATF officials said several of the 70-plus guns seized before Wednesday were linked to previous violent crimes. The guns confiscated Wednesday will be analyzed and checked against a national database to determine if they were used in other crimes and to try to trace their source, officials said.

"The investigation will continue. We already had a lot of guns in our custody, we know some of them are related to violent crimes," Chittum said. "I suspect we will get more hits. I don't think this is over yet."