creating solids for boolean operations

I have a closed triangulated surface that I would like to combine with other solids using boolean operations but the program crashes during the boolean operation. Could someone please tell me what I am doing wrong? I suspect that I am not creating the solid object correctly from my triangulated surface but I don't know if there is a better way to create a solid from a set of triangles.

I would greatly appreciate any help.

thanks,
-vivek

The following illustrates what I am doing:

// create a tetrahedron from points
//
// vertices->edges->wires->faces->shell
gp_Pnt v1(1, 0, 0);
gp_Pnt v2(0, 1, 0);
gp_Pnt v3(0, 0, 1);
gp_Pnt v4(0, 0, 0);

// first create edges
TopoDS_Edge e[6];
e[0] = BRepBuilderAPI_MakeEdge(v1,v4);
e[1] = BRepBuilderAPI_MakeEdge(v4,v2);
e[2] = BRepBuilderAPI_MakeEdge(v4,v3);
e[3] = BRepBuilderAPI_MakeEdge(v2,v1);
e[4] = BRepBuilderAPI_MakeEdge(v3,v2);
e[5] = BRepBuilderAPI_MakeEdge(v3,v1);

// now create wires
//
TopoDS_Wire w[4];
w[0] = BRepBuilderAPI_MakeWire(e[5], e[3], e[4]);
w[1] = BRepBuilderAPI_MakeWire(e[1], e[3], e[0]);
w[2] = BRepBuilderAPI_MakeWire(e[0], e[5], e[2]);
w[3] = BRepBuilderAPI_MakeWire(e[2], e[4], e[1]);

// use the above wires to create faces
//
TopoDS_Face f[4];
f[0] = BRepBuilderAPI_MakeFace(w[0]);
f[1] = BRepBuilderAPI_MakeFace(w[1]);
f[2] = BRepBuilderAPI_MakeFace(w[2]);
f[3] = BRepBuilderAPI_MakeFace(w[3]);

// sew the faces together to create a shell
//
BRepOffsetAPI_Sewing Sew;
for(int j=0; j Sew.Add(f[j]);

Sew.Perform();
TopoDS_Shape shell= Sew.SewedShape();

// create a solid box
//
gp_Pnt P(0,0,0);
TopoDS_Shape theBox = BRepPrimAPI_MakeBox(0.5,0.5,0.5);

// fuse the tetrahedron with the box
// -- this is where the program crashes
//
TopoDS_Shape FusedShape = BRepAlgoAPI_Fuse(theBox,shell);