In Brussels this week, two former U.S. drone technicians are speaking out against the aerial bombing program as the European Parliament gears up for a hearing on unmanned warfare and the U.S. prepares to confront its own legacy on drone strikes.

At an event with campaigners on Thursday, Cian Westmoreland and Lisa Ling, who worked on the military's drone technology systems, criticized the bombing program for what they say was a lack of recognition for human life.

Westmoreland first spoke out against the program in 2015 along with three other Air Force pilots, who published a letter accusing the Obama administration of "lying publicly" about the program and warning that "the innocent civilians we were killing only fueled the feelings of hatred that ignited terrorism and groups like ISIS."

On Thursday, he said he was compelled to come forward after being given an award for helping build a station in Kandahar, Afghanistan that contributed to 2,400 missions and 2,000 "enemy kills."

That made him feel "horrible," he told the Guardian.

"The connection needs to be made that if strategic and military goals are to be fulfilled, civilian lives must be respected," he said.

The Guardian notes that Britain is currently the only European country to use drones, but that the European Parliament believes that may change as more nations come under increasing pressure to support U.S. warfare.

The two whistleblowers also attended a parliamentary hearing on Thursday to discuss the impacts of drone warfare on civilian communities. Westmoreland said he noticed a "total disconnect" among many of the Members of European Parliament (MEPs) during the hearing, including during videotaped testimony from the brother of a cleric killed during a strike who talked about the impact it had on his family. "One of them was playing on their cellphone while this was going on," Westmoreland said.

Thursday's hearing also took place just a day before President Barack Obama is expected to announce the number of civilian casualties caused by U.S. drone strikes in nontraditional battlegrounds like Pakistan, Yemen, Somalia, and Libya since 2009, leaving out figures for active war zones like Iraq and Afghanistan.

A report released Thursday by the international human rights group Reprieve exposes the administration's misleading—and rare—public statements on civilian casualties from drone strikes.

Ling said the hearing felt like a first step toward "exploring issues of what does participation in the drone war or extrajudicial killing actually look like."

She added that she had been shocked by "how little the public knew" about the program. "As citizens we need to have some conversation about the things that are in the dark.... The people who are out of the picture are the people who are on the ground within the drone program, and the victims," she said.

"Humanity has been taken out of the decision: there has been a lot of talk about the plane itself and how cool the technology is," she added, "but not a lot of conversation about the people who are affected."