Exhibit 10.1

FIRST AMENDMENT TO STOCK PURCHASE AGREEMENT

THIS FIRST AMENDMENT TO STOCK PURCHASE AGREEMENT (“First Amendment”) is made
effective as of September 30, 2006, by and among (i) Federal Services
Acquisition Corporation, a Delaware corporation (“FSAC”); (ii) Advanced
Technology Systems, Inc., a Virginia corporation (“ATS”); (iii) Delmar Lewis,
Claude Rumsey and Harry Katrivanos as all of the shareholders of ATS
(collectively, the “Shareholders”); and (iv) Claude Rumsey in his capacity as
the Shareholders’ Representative (the “Shareholders’ Representative”).

RECITALS:

R-1.  By the terms of a Stock Purchase Agreement dated April 19, 2006 by and
among FSAC, ATS, the Shareholders and the Shareholders’ Representative (the
“Stock Purchase Agreement”), FSAC agreed to purchase from the Shareholders and
the Shareholders agreed to sell to FSAC all of the Shareholders respective
shares of ATS “Capital Stock” (as defined in the Stock Purchase Agreement)
pursuant to the terms and conditions contained therein.

R-2.  Section 10.1(b) of the Stock Purchase Agreement provides that either party
may terminate the Stock Purchase Agreement if the “Closing” (as defined in the
Stock Purchase Agreement) has not occurred by September 30, 2006 for any reason
other than a breach of the Stock Purchase Agreement by the terminating party.

R-3.  The undersigned wish to amend the Stock Purchase Agreement by this First
Amendment to extend from September 30, 2006 to November 30, 2006, the date
specified in Section 10.1(b) of the Stock Purchase Agreement.

NOW, THEREFORE, for good and valuable consideration, the receipt and sufficiency
of which is hereby acknowledged, the undersigned do hereby agree as follows:

1.  The reference to “September 30, 2006” in Section 10.1(b) of the Stock
Purchase Agreement is hereby deleted and replaced with “November 30, 2006.”

2.  This First Amendment shall in all respects be governed by, and construed in
accordance with, the laws (excluding conflict of laws, rules and principles) of
the Commonwealth of Virginia applicable to agreements made and to be performed
entirely within the Commonwealth of Virginia, including all matters of
construction, validity and performance.

3.  Except as specifically amended by this First Amendment, the Stock Purchase
Agreement is unmodified and in full force and effect and is hereby ratified and
affirmed by the undersigned.

This First Amendment may be executed in several counterparts, all of which taken
together shall be deemed one and constitute a single instrument.  Any manual
signature upon this First Amendment that is faxed, scanned or photocopied shall
for all purposes have the same validity, effect and admissibility in evidence as
an original signature and the parties hereby waive any objection to the
contrary.

1

--------------------------------------------------------------------------------

IN WITNESS WHEREOF, each of the parties hereto has caused this First Amendment
to be duly executed and delivered in its name and on its behalf, all as of the
day and year first above written.

 

FEDERAL SERVICES

 

 

ACQUISITION CORPORATION,

 

 

a Delaware corporation

 

 

 

 

 

 

 

 

 

 

 

 

By:

 

/s/ Peter M. Schulte

 

 

Name:

 

Peter M. Schulte

 

 

Title:

 

President

 

 

 

 

 

 

 

 

 

 

 

 

ADVANCED TECHNOLOGY

 

 

SYSTEMS, INC.,

 

 

a Virginia corporation

 

 

 

 

 

 

 

 

 

 

 

 

By:

 

/s/ Claude Rumsey

 

 

Name:

 

Claude Rumsey

 

 

Title:

 

Vice-Chairman

 

 

 

 

 

 

 

 

 

 

 

 

SHAREHOLDERS:

 

 

 

 

 

 

 

 

 

 

 

 

/s/ Delmar Lewis

 

 

Delmar Lewis

 

 

 

 

 

 

 

 

 

 

 

 

/s/ Claude Rumsey

 

 

Claude Rumsey

 

 

 

 

 

 

 

 

 

 

 

 

/s/ Harry Katrivanos

 

 

Harry Katrivanos

 

2

--------------------------------------------------------------------------------

 

 

SHAREHOLDERS’ REPRESENTATIVE:

 

 

 

 

 

 

 

 

 

 

 

 

/s/ Claude Rumsey

 

 

Claude Rumsey

 

3

--------------------------------------------------------------------------------