Cullen said the community was “absolutely heartbroken”.
“They were really part of the community, part of the fabric of the community and how sadly they will all be missed by their wee friends and of course their mother will be sadly missed by this community as well,” the Sinn Féin MP said.
She said it is important that people do not speculate about the incident.
“Let’s deal with the facts when they come out and when those facts are made known, then we can have conversations, but until then, it is really important with respect for the family, the wider community and the emergency services that we don’t speculate,” Cullen said.
Ulster Unionist peer Lord Elliott said the incident was devastating.
“The family is so local and because the wider family is so well known, it’s just devastating, people are really finding it difficult to get their head around this and that this actually happened,” he said.
Police remain at the scene on Thursday morning.
The road is likely to be closed for some time while officers continue to gather evidence, BBC News NI understands.